Internal combustion engines are supplied with a mixture of air and fuel for combustion within the engine that generates mechanical power. To maximize the power generated by this combustion process, the engine is often equipped with a turbocharged air induction system.
A turbocharged air induction system includes a turbocharger that uses exhaust from the engine to compress air flowing into the engine, thereby forcing more air into a combustion chamber of the engine than the engine could otherwise draw into the combustion chamber. This increased supply of air allows for increased fuelling, resulting in an increased engine power output.
The fuel energy conversion efficiency of an engine may depend on many factors, including the efficiency of the engine's turbocharger. Turbocharger efficiency can be affected by the structures at the turbine operating to extract energy from the exhaust gas, as well as the structures at the compressor operating to use the extracted energy to compress air that is provided to the engine cylinders.
Various past attempts have been made to increase the efficiency of turbochargers by improving, in part, the operating efficiency of the compressor by adjusting design features of the compressor's impeller. One example of a compressor impeller can be found in DE102009007843A1 (the '843 reference), which describes a compressor wheel having a set of split blades arranged between two consecutive complete blades. As show in the '843 reference, for example, in FIGS. 1 and 2, the compressor wheel includes a longer blade and a shorter blade arranged between full-length blades, in that order, relative to a direction of rotation of the compressor wheel (from right to left as shown in FIG. 2). However, the compressor wheel arrangements described in the '843 patent may only partially achieve considerable efficiency increases for certain frame sizes of compressors, and also for certain compressor wheel sizes, and may not be suitable for large displacement engines that require large amounts of air to pass through the compressor, while also still maintaining acceptable low-end performance.